Recombinant scFv antibodies against E protein and N protein of severe acute respiratory syndrome virus.

Three single chain antibodies (scFv) against the proteins of severe acute respiratory syndrome coronavirus (SARS-CoV) were isolated by phage display from an scFv antibody library. Bio-panning was carried out against immobilized purified envelope (E) and nucleocapsid (N) proteins of SARS-CoV. Their binding activity and specificity to E or N protein of SARS-CoV were characterized by phage-ELISA. Two of them, B10 and C20, could recognize non-overlapping epitopes of the E protein according to the two-site binding test result. Clone A17 could recognize N protein. The sequence of the epitope or overlapping epitope of scFv antibody A17 was PTDSTDNNQNGGRNGARPKQRRPQ. The affinity (equilibrium dissociation constant, K(d)) of SARS-CoV E protein was 5.7 x 10(-8) M for B10 and 8.9 x 10(-8) M for C20. The affinity of A17 for N protein was 2.1 x 10(-6) M. All three scFv antibodies were purified with affinity chromatography and determined by Western blot.